www.pudn.com > mediator15src.zip > decode.c

/*  
 * Mpeg Layer-1,2,3 audio decoder  
 * ------------------------------ 
 * copyright (c) 1995,1996,1997 by Michael Hipp, All rights reserved. 
 * See also 'README' 
 * 
 */ 
 
#include "mpg123.h" 
 
#define WRITE_SAMPLE(samples,sum) \ 
  if( (sum) > 32767.0) { *(samples) = 0x7fff; } \ 
  else if( (sum) < -32768.0) { *(samples) = -0x8000; } \ 
  else { *(samples) = (short)sum; } 
 
void synth_1to1_mono(float *bandPtr, unsigned char *samples, int *pnt) 
{ 
  short samples_tmp[64]; 
  short *tmp1 = samples_tmp; 
  int i; 
  int pnt1 = 0; 
 
  synth_1to1(bandPtr, 0, (unsigned char *)samples_tmp, &pnt1); 
  samples += *pnt; 
 
  for(i = 0; i < 32; i++) { 
    *((short *)samples) = *tmp1; 
    samples += 2; 
    tmp1 += 2; 
  } 
  *pnt += 64; 
 
  return; 
} 
 
int bo; 
 
 
void synth_1to1(float *bandPtr, int channel, unsigned char *out, int *pnt) 
{ 
  static float buffs[2][2][0x110]; 
  static const int step = 2; 
  short *samples = (short *)(out + *pnt); 
 
  float *b0, (*buf)[0x110]; 
  int bo1; 
 
  if(!channel) { 
    bo--; 
    bo &= 0xf; 
    buf = buffs[0]; 
  } 
  else { 
    samples++; 
    buf = buffs[1]; 
  } 
 
  if (bo & 0x1) { 
    b0 = buf[0]; 
    bo1 = bo; 
    dct64(buf[1] + ((bo + 1) & 0xf), buf[0] + bo, bandPtr); 
  } 
  else { 
    b0 = buf[1]; 
    bo1 = bo + 1; 
    dct64(buf[0] + bo, buf[1] + bo + 1, bandPtr); 
  } 
 
  { 
    register int j; 
    float *window = decwin + 16 - bo1; 
  
    for (j = 16; j; j--, window += 0x10, samples += step) 
    { 
      float sum; 
      sum  = *window++ * *b0++; 
      sum -= *window++ * *b0++; 
      sum += *window++ * *b0++; 
      sum -= *window++ * *b0++; 
      sum += *window++ * *b0++; 
      sum -= *window++ * *b0++; 
      sum += *window++ * *b0++; 
      sum -= *window++ * *b0++; 
      sum += *window++ * *b0++; 
      sum -= *window++ * *b0++; 
      sum += *window++ * *b0++; 
      sum -= *window++ * *b0++; 
      sum += *window++ * *b0++; 
      sum -= *window++ * *b0++; 
      sum += *window++ * *b0++; 
      sum -= *window++ * *b0++; 
 
      WRITE_SAMPLE(samples, sum); 
    } 
 
    { 
      float sum; 
      sum  = window[0x0] * b0[0x0]; 
      sum += window[0x2] * b0[0x2]; 
      sum += window[0x4] * b0[0x4]; 
      sum += window[0x6] * b0[0x6]; 
      sum += window[0x8] * b0[0x8]; 
      sum += window[0xA] * b0[0xA]; 
      sum += window[0xC] * b0[0xC]; 
      sum += window[0xE] * b0[0xE]; 
      WRITE_SAMPLE(samples, sum); 
      b0 -= 0x10, window -= 0x20, samples += step; 
    } 
    window += bo1 << 1; 
 
    for (j = 15; j; j--, b0 -= 0x20, window -= 0x10, samples += step) 
    { 
      float sum; 
      sum = -*(--window) * *b0++; 
      sum -= *(--window) * *b0++; 
      sum -= *(--window) * *b0++; 
      sum -= *(--window) * *b0++; 
      sum -= *(--window) * *b0++; 
      sum -= *(--window) * *b0++; 
      sum -= *(--window) * *b0++; 
      sum -= *(--window) * *b0++; 
      sum -= *(--window) * *b0++; 
      sum -= *(--window) * *b0++; 
      sum -= *(--window) * *b0++; 
      sum -= *(--window) * *b0++; 
      sum -= *(--window) * *b0++; 
      sum -= *(--window) * *b0++; 
      sum -= *(--window) * *b0++; 
      sum -= *(--window) * *b0++; 
      WRITE_SAMPLE(samples, sum); 
    } 
  } 
  *pnt += 128; 
  return; 
}